title: Detection and quantification of focal uptake in head and neck tumours: (18)F-FDG PET/MR versus PET/CT.
abstract: OBJECTIVE
  Our objectives were to assess the quality of PET images and coregistered anatomic images obtained with PET/MR, to evaluate the detection of focal uptake and SUV, and to compare these findings with those of PET/CT in patients with head and neck tumours.
  
  
  METHODS
  The study group comprised 32 consecutive patients with malignant head and neck tumours who underwent whole-body (18)F-FDG PET/MR and PET/CT. PET images were reconstructed using the attenuation correction sequence for PET/MR and CT for PET/CT. Two experienced observers evaluated the anonymized data. They evaluated image and fusion quality, lesion conspicuity, anatomic location, number and size of categorized (benign versus assumed malignant) lesions with focal uptake. Region of interest (ROI) analysis was performed to determine SUVs of lesions and organs for both modalities. Statistical analysis considered data clustering due to multiple lesions per patient.
  
  
  RESULTS
  PET/MR coregistration and image fusion was feasible in all patients. The analysis included 66 malignant lesions (tumours, metastatic lymph nodes and distant metastases), 136 benign lesions and 470 organ ROIs. There was no statistically significant difference between PET/MR and PET/CT regarding rating scores for image quality, fusion quality, lesion conspicuity or anatomic location, number of detected lesions and number of patients with and without malignant lesions. A high correlation was observed for SUVmean and SUVmax measured on PET/MR and PET/CT for malignant lesions, benign lesions and organs (ρ = 0.787 to 0.877, p < 0.001). SUVmean and SUVmax measured on PET/MR were significantly lower than on PET/CT for malignant tumours, metastatic neck nodes, benign lesions, bone marrow, and liver (p < 0.05). The main factor affecting the difference between SUVs in malignant lesions was tumour size (p < 0.01).
  
  
  CONCLUSIONS
  In patients with head and neck tumours, PET/MR showed equivalent performance to PET/CT in terms of qualitative results. Comparison of SUVs revealed an excellent correlation for measurements on both modalities, but underestimation of SUVs measured on PET/MR as compared to PET/CT.
authors.affiliation: Department of Imaging, Divisions of Radiology and Nuclear Medicine, Geneva University Hospital, Rue Gabrielle Perret Gentil 4, CH-1211, Geneva 14, Switzerland.
authors.forename: Arthur
authors.initials: A
authors.lastname: Varoquaux
authors.forename: Olivier
authors.initials: O
authors.lastname: Rager
authors.forename: Antoine
authors.initials: A
authors.lastname: Poncet
authors.forename: Bénédicte M A
authors.initials: BM
authors.lastname: Delattre
authors.forename: Osman
authors.initials: O
authors.lastname: Ratib
authors.forename: Christoph D
authors.initials: CD
authors.lastname: Becker
authors.forename: Pavel
authors.initials: P
authors.lastname: Dulguerov
authors.forename: Nicolas
authors.initials: N
authors.lastname: Dulguerov
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
authors.forename: Minerva
authors.initials: M
authors.lastname: Becker
mesh_terms: D000328:Adult; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006258:Head and Neck Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18